1. Field of the Invention
The present invention relates generally to storage area networks. Particularly, the present invention relates to operation of storage area networks with attached hosts running virtualization software and having a plurality of virtual machines.
2. Description of the Related Art
Virtual machines (VMs) are being used in increasing numbers in networks. They are advantageous because they maximize the use of the hardware resources in the network, particularly the host or server hardware. However, the use of virtual machines presents problems when the host machine is connected to a storage area network (SAN). For a number of reasons it is desirable to have visibility of the particular virtual machines in the various hosts on the SAN. These reasons include simplified management through the use of a single management tool, cost back charging relating to resource use, service level agreement enforcement, isolation and improved quality of service (QoS) or prioritization of the communications for given VMs.
Current VM hypervisors do not readily provide this capability. For example, in VMware, the VMs can be separately identified on the SAN if they use the NPIV features provided by the host bus adaptors (HBAs). But to use NPIV, the VM must be setup to use raw device mapping (RDM) of the hypervisor. This results in management difficulties in both the hypervisor and on the SAN. On the SAN, zoning becomes very complicated as each VM must be operated on individually. Similarly, SAN QoS is also more difficult to manage because of the individual nature of the VMs and their NPIV addresses. In addition, as the environment scales up, the problems increase at a greater rate.
VMware ESX, the prevalent hypervisor, provides an alternate technique referred to as VMFS or virtual machine file system. It is much easier to administer VMs when VMFS is used, so the majority of server administrators would prefer to utilize VMFS. But VMFS does not allow identification on the SAN of the individual VMs. Currently NPIV cannot be used, even with its attendant SAN management issues. So the inability to manage, charge back and so on has limited the use of hypervisors using VMFS operation on the SAN.
Similar issues are present with Hyper-V from Microsoft and its clustered shared volume (CSV) file system and XenServer from Citrix with the Control Domain and Storage Repositories.
As VMFS or CSV, depending on the hypervisor, is the greatly preferred technique for providing storage resources in a hypervisor, it would be desirable to be able to better operate with VMFS or CSV-based systems on a SAN.